Method of handling a mobility management back-off timer and related communication device

ABSTRACT

A method of handling a mobility management back-off timer for a mobile device in a wireless communication system comprises performing a mobility management procedure in response to a paging signaling transmitted by a network of the wireless communication system; and stopping the mobility management back-off timer after performing an authentication procedure in the mobility management procedure successfully.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is a divisional application of U.S. application Ser.No. 13/561,087, filed on Jul. 30, 2012, which claims the benefit of U.S.Provisional Application No. 61/512,922, filed on Jul. 29, 2011 andentitled “Method to handling of back off timer in case of networkinitiated procedure”.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a method used in a wirelesscommunication system and related communication device, and moreparticularly, to a method of handling a mobility management back-offtimer and related communication device.

2. Description of the Prior Art

The 3rd Generation Partnership Project (3GPP) has developed a universalmobile telecommunications system (UMTS) which adopts a wideband codedivision multiple access (WCDMA) as a wireless air interface. In theUMTS, a radio access network known as a universal terrestrial radioaccess network (UTRAN) includes multiple Node-Bs (NBs) for communicatingwith multiple user equipments (UEs) (i.e., mobile stations (MSs)). As asuccessor of a General Packet Radio Service (GPRS) system, the UMTSprovides high frequency spectrum utilization, universal coverage, andhigh-speed multimedia data transmission which are beneficial for the UEsand the NBs of the UMTS. Please note that, the UMTS and the GPRS systemcan support both a packet-switch (PS) service and a circuit-switch (CS)service, while systems older than the GPRS system support only the CSservice.

A long-term evolution (LTE) system supporting the 3GPP Rel-8 standardand/or the 3GPP Rel-9 standard are developed by the 3GPP as a successorof the UMTS, for further enhancing performance of the UMTS to satisfyincreasing needs of users. The LTE system includes a new radio interfaceand a new radio network architecture that provides a high data rate, lowlatency, packet optimization, and improved system capacity and coverage.In the LTE system, a radio access network known as an evolved UTRAN(E-UTRAN) includes multiple evolved Node-Bs (eNBs) for communicatingwith multiple UEs, and communicating with a core network (e.g., evolvedpacket core (EPC) network) including a mobility management entity (MME),a serving gateway, etc., for Non Access Stratum (NAS) control.

A LTE-advanced (LTE-A) system, as its name implies, is an evolution ofthe LTE system. The LTE-A system targets faster switching between powerstates, improves performance at the coverage edge of an eNB, andincludes advanced techniques, such as carrier aggregation (CA),coordinated multipoint transmission/reception (CoMP), uplink (UL)multiple-input multiple-output (MIMO), etc. For a UE and an eNB tocommunicate with each other in the LTE-A system, the UE and the eNB mustsupport standards developed for the LTE-A system, such as the 3GPPRel-10 standard or later versions.

In the abovementioned systems, congestion of a network (i.e., the radioaccess network and/or the core network) can be controlled by using amobility management back-off timer. That is, when a UE transmits asignaling (e.g., for initiating a procedure/session) to the network, thenetwork replies a rejection signaling including the mobility managementback-off timer if the network is in congestion. The UE can retransmitthe signaling, after the mobility management back-off timer expires(i.e., stops running). Alternatively, the UE can stop the mobilitymanagement back-off timer, when the network transmits a paging signaling(e.g., for initiating a procedure/session) to the UE. That is, themobility management back-off timer can be stopped by thenetwork-initiated procedure.

However, when a fake network (e.g., fake eNB or fake core network)transmits paging signalings (i.e., fake signalings) to UEs, the UEs maystop mobility management back-off timers and start to perform procedurescorresponding to the paging signalings. Then, the congestion of thenetwork (i.e., the true network) is deteriorated, and the network cannot operate regularly for a long time.

On the other hand, a UE is allowed to initiate an emergency session(e.g., for making an emergency call), when the mobility managementback-off timer is running (i.e., not expired). During the emergencysession, it is possible that the congestion of the network is mitigatedor eliminated, and the network may initiate a session managementprocedure for an access point name (APN) with the UE. In this situation,since the mobility management back-off timer is still running, and theUE cannot respond to the session management procedure, i.e., replyingone or more signalings for performing the session management procedure.Thus, the UE may loss ongoing radio bearer when changing a routing area.Alternatively, the UE cannot resume a service after the emergencysession, since the mobility management back-off timer is not stopped.

Therefore, how to solve abovementioned problems is a topic to bediscussed and addressed.

SUMMARY OF THE INVENTION

The present invention therefore provides a method and relatedcommunication device for handling a mobility management back-off timerto solve the abovementioned problem.

A method of handling a mobility management back-off timer for a mobiledevice in a wireless communication system is disclosed. The methodcomprises performing a mobility management procedure in response to apaging signaling transmitted by a network of the wireless communicationsystem; and stopping the mobility management back-off timer afterperforming an authentication procedure in the mobility managementprocedure successfully.

These and other objectives of the present invention will no doubt becomeobvious to those of ordinary skill in the art after reading thefollowing detailed description of the preferred embodiment that isillustrated in the various figures and drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic diagram of a wireless communication systemaccording to an example of the present invention.

FIG. 2 is a schematic diagram of a communication device according to anexample of the present invention.

FIG. 3 is a flowchart of a process according to an example of thepresent invention.

FIG. 4 is a flowchart of a process according to an example of thepresent invention.

DETAILED DESCRIPTION

Please refer to FIG. 1, which is a schematic diagram of a wirelesscommunication system 10 according to an example of the presentinvention. The wireless communication system 10 is briefly composed of anetwork and a plurality of user equipments (UEs). In FIG. 1, the networkand the UEs are simply utilized for illustrating the structure of thewireless communication system 10. Practically, the network can be auniversal terrestrial radio access network (UTRAN) comprising aplurality of Node-Bs (NBs) in a universal mobile telecommunicationssystem (UMTS). Alternatively, the network can be an evolved UTRAN(E-UTRAN) comprising a plurality of evolved NBs (eNBs) and/or relays inalong term evolution (LTE) system or a LTE-Advanced (LTE-A) system.

Furthermore, the network can also include both the UTRAN/E-UTRAN and acore network (e.g., an evolved packet core (EPC) network), wherein thecore network includes network entities such as a Mobility ManagementEntity (MME), a Serving Gateway (S-GW), a Packet Data Network (PDN)Gateway (P-GW), and/or a local gateway (L-GW). In other words, after thenetwork receives information (e.g., message, signaling and/or packet)transmitted by a UE, the information may be processed only by theUTRAN/E-UTRAN and decisions corresponding to the information are made atthe UTRAN/E-UTRAN. Alternatively, the UTRAN/E-UTRAN may forward theinformation to the core network, and the decisions corresponding to theinformation are made at the core network after the core networkprocesses the information. Besides, the information can be processed byboth the UTRAN/E-UTRAN and the core network, and the decisions are madeafter coordination and/or cooperation are performed by the UTRAN/E-UTRANand the core network.

Please refer to FIG. 2, which is a schematic diagram of a communicationdevice 20 according to an example of the present invention. Thecommunication device 20 can be a UE or the network shown in FIG. 1, butis not limited herein. The communication device 20 may include aprocessing means 200 such as a microprocessor or an Application SpecificIntegrated Circuit (ASIC), a storage unit 210 and a communicationinterfacing unit 220. The storage unit 210 may be any data storagedevice that can store a program code 214, accessed by the processingmeans 200. Examples of the storage unit 210 include but are not limitedto a subscriber identity module (SIM), read-only memory (ROM), flashmemory, random-access memory (RAM), CD-ROM/DVD-ROM, magnetic tape, harddisk, and optical data storage device. The communication interfacingunit 220 is preferably a radio transceiver, and can transmit and receivewireless signals according to processing results of the processing means200.

Please refer to FIG. 3, which is a flowchart of a process 30 accordingto an example of the present invention. The process 30 is utilized in aUE shown in FIG. 1, for handling a mobility management back-off timer.The process 30 may be compiled into the program code 214 and includesthe following steps:

Step 300: Start.

Step 302: Perform a mobility management procedure in response to apaging signaling transmitted by the network.

Step 304: Stop the mobility management back-off timer after performingan authentication procedure in the mobility management proceduresuccessfully.

Step 306: End.

According to the process 30, after the UE receives a paging signalingtransmitted by the network, the UE performs a mobility managementprocedure in response to the paging signaling. The UE stops the mobilitymanagement back-off timer after performing an authentication procedurein the mobility management procedure successfully. That is, the UE doesnot simply stops the mobility management back-off timer after receivingthe paging signaling but stops the mobility management back-off timerafter performing the authentication procedure successfully during themobility management procedure. Thus, the UE will not stop the mobilitymanagement back-off timer in response to a paging signaling transmittedby a fake network, i.e., a fake signaling. As a result, congestion ofthe network will not be deteriorated.

Please note that, realization of the process 30 is not limited. Forexample, the mobility management back-off timer is a T3246 timer or aT3346 timer defined in the 3GPP standard. Further, the UE can determinethat the authentication procedure is performed successfully, afterreceiving a security mode command from the network, for enabling aplurality of security parameters obtained during the authenticationprocedure. Besides, the UE can keep the mobility management back-offtimer running, if the authentication procedure is not performedsuccessfully, e.g., the UE determines that the paging signaling istransmitted by a fake network. For example, the UE can store a remainingtime of the mobility management back-off timer, after receiving thepaging signaling. Then, the UE restarts the mobility management back-offtimer with the remaining time, if the authentication procedure is notperformed successfully.

Thus, according to the process 30 and the above description, the UE canhandle the mobility management back-off timer properly whether theauthentication procedure is performed successfully.

Please refer to FIG. 4, which is a flowchart of a process 40 accordingto an example of the present invention. The process 40 is utilized in aUE shown in FIG. 1, for handling a mobility management back-off timer.The process 40 may be compiled into the program code 214 and includesthe following steps:

Step 400: Start.

Step 402: Initiate an emergency session with the network, when themobility management back-off timer is running.

Step 404: Stop the mobility management back-off timer, when the networkinitiates a session management procedure for an access point name (APN)with the UE during the emergency session.

Step 406: End.

According to the process 40, the UE initiates an emergency session(e.g., for an emergency call) with the network during that the mobilitymanagement back-off timer is running. If the network initiates a sessionmanagement procedure for an APN (i.e., for establishing a packet dataprotocol (PDP) context for the APN) with the UE during the emergencysession, the UE stops the mobility management back-off timer. Forexample, the network may initiate the session management procedure withthe UE by sending a session management signaling to the UE. The UE stopsthe mobility management back-off timer after receiving the sessionmanagement signaling. Further, the UE can transmit a session managementresponse to the network when the emergency session is completed (or evenduring the emergency session), for responding to the session managementsignaling. The mobility management back-off timer can be a T3346 timerdefined in the 3GPP standard. For example, the network may initiate thesession management procedure with the UE by sending a session managementsignaling to the UE. The UE stops the mobility management back-off timerafter receiving the session management signaling. Further, the UE cantransmit a session management response to the network when the emergencysession is completed (or even during the emergency session), forresponding to the session management signaling. The mobility managementback-off timer can be a T3346 timer defined in the 3GPP standard.

Thus, according to the process 40 and the above description, the UE willnot loss ongoing radio bearer when changing a routing area during theemergency session. Besides, the UE can resume a service during theemergency session, since the mobility management back-off timer isstopped.

Those skilled in the art should readily make combinations, modificationsand/or alterations on the abovementioned examples. The abovementionedsteps of the processes including suggested steps can be realized bymeans that could be a hardware, a firmware known as a combination of ahardware device and computer instructions and data that reside asread-only software on the hardware device, or an electronic system.Examples of hardware can include analog, digital and mixed circuitsknown as microcircuit, microchip, or silicon chip. Examples of theelectronic system can include a system on chip (SOC), system in package(SiP), a computer on module (COM), and the communication device 20.

To sum up, the present invention provides a method of handling amobility management back-off timer. A problem that a fake network maytransmit a paging signaling to a UE to stop the mobility managementback-off timer of the UE is solved. Besides, a problem that a UE mayloss ongoing bearer and services during an emergency session due to themobility management back-off timer is also solved.

Those skilled in the art will readily observe that numerousmodifications and alterations of the device and method may be made whileretaining the teachings of the invention. Accordingly, the abovedisclosure should be construed as limited only by the metes and boundsof the appended claims.

What is claimed is:
 1. A method of handling a mobility managementback-off timer for a mobile device in a wireless communication system,the method comprising: performing a mobility management procedure inresponse to a paging signaling transmitted by a network of the wirelesscommunication system; storing a remaining time of the mobilitymanagement back-off timer, after receiving the paging signaling;stopping the mobility management back-off timer only when anauthentication procedure is successfully performed in the mobilitymanagement procedure; and restarting the mobility management back-offtimer according to the remaining time, if the authentication procedureis not performed successfully.
 2. The method of claim 1, wherein themobility management back-off timer is a T3246 timer or a T3346 timerdefined in the 3rd Generation Partnership Project (3GPP) standard. 3.The method of claim 1, wherein the mobile device determines that theauthentication procedure is performed successfully, after receiving asecurity mode command from the network, for enabling a plurality ofsecurity parameters obtained during the authentication procedure.